Reduction of dustiness and abrading of soft porous low density hydrated calcium silicate products

ABSTRACT

Means of diminishing surface dusting in porous low density hydrated calcium silicate bodies and improving resistance to abrasion and crumbling of their soft, friable texture by depositing thereon a high temperature melting wax, and the dustfree and more durable wax containing hydrated calcium silicate products.

United States Patent Hurley 51 May 9, 1972 [54] REDUCTION OF DUSTINESSAND [56] References Cited ABRADING OF SOFT POROUS LOW UNITED STATESPATENTS DENSITY HYDRATED CALCIUM SILIC TE PRODUCTS 3,007,812 11/1961Smith et a1. ..1 17/123 G 2,504,920 4/1950 Buckman et a1. ....1 17/123 C[72] Inventor: Elmer Brewington Hurley, Martinsville, 3,257,220 6/1966Kalousek ..23/1 10 R Primary E.\'anzinerTheodore Morris [73] Asslgnee..Lolzfns-Manvflle Corporation, New York, Atmmey J0hn A. McKinney andRobert M. Krone [22] Filed: Mar. 31, 1970 [57] ABSTRACT [21] App1.No.:24,328 Means of diminishing surface dusting in porous low densityhydrated calcium silicate bodies and improving resistance to abrasionand crumbling of their soft, friable texture by [52] us Cl '106/272,117N23- 252/88 depositing thereon a high temperature melting wax, andthe [51] II!!- Cl. ..C08h 9/06 dust free and more durable wax containinghydrated calcium [58] Field of Search 106/272, 271, 270; 252/88;Silicate products.

117/123, 126 AO;23/llOR 10 Claims, No Drawings BACKGROUND OF THEINVENTION Low density hydrated calcium silicate materials such as havecommonly long been employed as thermal insulations, high temperatureresistance construction materials, safe fillers, flame resistantpartition barriers, and related products, are of relatively soft andhighly porous compositions presenting a friable and loosely coherenttexture which is dusty upon handling, abrades or crumbles to powderthereby creating a health hazard as well as the other undesirableeffects of dust, and is lacking desirable durability in being especiallysusceptible to abrasion, chipping, and general breakage.

SUMMARY OF THE INVENTION This invention comprises a method of reducingdustiness and increasing durability of soft and porous, low densityhydrated calcium silicates, and the improved product havingsubstantially dust-free surfaces of superior resistance to abrasion,crumbling, chipping and breakage attained through the application of awax having a high temperature melting point.

It is the primary objective of this invention to improve the handlingcharacteristics of typical low density bodies comprising hydratedcalcium silicates in effectively reducing their surface dusting andtendency to abrade or crumble into powder, minimize any potential healthdanger through dust inhalation or contact, and enhance their durabilityand resistance to abrasion, chipping, and breakage.

DESCRIPTION OF THE PREFERRED EMBODIMENT This invention provides means ofenhancing the handling and durability of relatively light weight bodiescomprising hydrated calcium silicate compositions which have for manyyears been commonly utilized as thermal insulating materials, among manyother related applications in the art. These hydrated calcium silicatesare normally produced by a heat induced reaction between lime andsilicate in the presence of water or water vapor wherein the lime andsilicate and water I combined in varying proportions and in turn producevarious compositions depending, for example, upon the relative ratio ofreactive ingredients and the degree of their reactivity, the time andtemperature of the reaction, all pursuant to wellknown and understoodknowledge of the art. To provide optimum insulating properties andresistance to high temperatures, etc., the hydrated calcium silicateproducts are generally formed in relatively low densities and in turn avery high degree of porosity, as is evident from the substantial weightof the ingredients in relation to the weight of the body of the product,for example, product densities of between about 5 and about 30 poundsper cubic foot, and typically about 8 to 16 pounds per cubic foot forcommon commercial thermal insulations. To strengthen the generally weakand loosely coherent consistency due to such high porosity or limitedstructural matrix of these materials, reinforcing fibrous materials aretypically included, such as asbestos, glass fiber or the like staplefibers having temperature resistance commensurate with the intendedapplication. The fibrous reinforcement, although significantly enhancingthe flexural strength and other structural strength requirements,nevertheless does not particularly contribute to composition hardnessand in turn resistance to fine particles or dust being abradedtherefrom, or their generally dusty nature. A typical calcium silicatethermal insulation product of the type to which this invention isdirected comprises that disclosed in US. Pat. No. 2,699,097 to Binkley,and related prior art patent disclosures. In carrying out thisinvention, the low density hydrated calcium silicate materials aretreated by applying to their surface, and in particular the exteriorproduct surface with regard to their intended application, a wax havinga high temperature melting point and in the form of emulsion with waterbeing the continuous phase. In applying the wax emulsified in water toterstices of the calcium silicate matrix by the wicking affect ofcapillary action leaving the wax material deposited noncontinuously onthe surface and just within open pores immediately adjacent thereto. Thewax thus applied does not form a continuous or impervious coating but aninterrupted and porous deposition. To achieve an effective noncontinuousdeposition and optimum application the oil-in-water type emulsion of waxshould be about 20 to about 30 percent by weight of the wax solids ofthe total emulsion weight. The suspending water content of the emulsioncan thereafter be removed from the material back through thediscontinuous wax deposition by normal evaporation at ambientconditions, or removal accelerated by exposure to elevated temperaturesor dry atmosphere.

To perform effectively the wax must be of a relatively high meltingpoint of at least about F. Further, it should be applied in amounts ofabout 0.1 gram to about 0.5 gram of wax solids per square foot surfacearea for a typical hydrated calcium silicate composition texture of adensity of about 10 to 14 pounds per cubic foot. Suitable waxes of aptproperties for use in this invention include, but are not limited to,montan wax, a mineral wax melting at about 184 E; vegetable waxescomprising ouricury wax (M.P. l79-l83 E), palm wax (M.P. 170-l75 F.),and sugar cane wax (M.P. l65-l80 F.); or castorwax, a synthetic materialproduced by the hydrogenation of castor oil, with a melting point ofabout 187 F. Montan wax is preferred.

Application techniques include any suitable means of handling andapplying oilin-water type emulsions such as commercial spray devices,brushing or simple immersion and the like routine means of administeringa liquid. Spray application is preferred since the amounts applied canmore easily be controlled and economically maintained at approximatelythe minimum effective proportion of about 0.1 gram of wax per squarefoot surface area whereas immersion application typically results inhigher and thus less economical deposition in proportions of about 0.5gram of wax per square foot of surface area.

In a typical application of this invention, hydrated calcium silicateproduct sold under the Johns-Manville Corporation trademark ofTHERMOBESTOS, and produced pursuant to the technique of the aforesaidBinkley US. Pat. No. 2,699,097 in the form of the usual half sections ofcylindrical pipe insulation units of a highly porous consistency of anapproximate ll pounds per cubic foot density mass, were treated on theirouter peripherial surface as follows. An emulsion of montan wax in acontinuous water phase containing approximately 25 percent by weight ofwax solids based upon the total emulsion, was spray applied to the outerperipherial surface of the hydrated calcium silicate half cylindricalsections in amount to deposit thereon about 0.1 gram per square footsurface area. The water content quickly wicked inwardly into thecapillary like interstices leaving on the surface a discontinuous orperforate wax deposition. The suspending water of emulsion wasthereafter removed by air drying.

This relatively simple and economical treatment converted the treatedsurface of the otherwise highly dusty and crumbling to powder, soft andfriable texture, to an essentially dust and powder-free condition whichresisted abrading away of fine particles or dust, and affected apronounced improvement in the durability of the surface withstandingabrading encountered in normal and even rough handling in contact withhard rough surfaces including a significant reduction in chipping andbreakage in the otherwise relatively soft and friable materialattributable to the very low density requirements for effective thennalinsulating characteristics. This treatment is particularly significantand beneficial in overcoming the potential hazards of physical contactwith asbestos and dust therefrom since asbestos is most commonlyincluded in such products as reinforcement, and silica containing dustderived from the calcium silicate material itself.

I Claim:

l. A method of reducing dustiness and increasing durability in a softand porous low density body comprising applying to the surface of a softand porous low density hydrated calcium silicate body an emulsion ofapproximately 20 to approximately 30 percent by weight of wax solids inwater, said wax having a melting point of at least about 170 F. andapplied in amounts of about 0.1 to about 0.5 gram per square foot ofsurface area.

2. The method of claim 1 wherein the soft and porous body compriseshydrated calcium silicate of a density of from about 5 to about 30pounds per cubic foot and wherein said wax is selected from the groupconsisting of montan wax, ouricury wax, palm wax, sugar cane wax and awax produced by the hydrogenation of castor oil.

3. The method of claim 2 wherein the emulsion of wax in water is appliedby spraying.

4. The method of claim 2 wherein the emulsion of wax is applied byimmersion.

5. The method of claim 1 wherein the hydrated calcium silicate body isof a density of about 8 to about 16 pounds per cubic foot.

6. The method of claim 1 wherein the said wax is montan wax.

7. A soft and porous low density body comprising hydrated calciumsilicate having on a surface thereof a noncontinuous deposition of waxhaving a melting point of at least about F. and in amounts of about 0.1to about 0.5 gram per square foot of said surface area.

8. The soft and porous low density body of claim 7 which compriseshydrated calcium silicate of a density of about 5 to 30 pounds per cubicfoot and comprises up to about 25 percent of reinforcing asbestos fiberand wherein said wax is selected from the group consisting of montanwax, ouricury wax, palm wax, sugar cane wax and a wax produced by thehydrogenation of castor oil.

9. The soft and porous low density hydrated calcium silicate body ofclaim 7 which is of a density of about 8 to 16 pounds per cubic foot andcomprises reinforcing fiber.

10. The soft and porous low density hydrated calcium silicate body ofclaim 7 wherein the wax applied is montan wax.

2. The method of claim 1 wherein the soft and porous body compriseshydrated calcium silicate of a density of from about 5 to about 30pounds per cubic foot and wherein said wax is selected from the groupconsisting of montan wax, ouricury wax, palm wax, sugar cane wax and awax produced by the hydrogenation of castor oil.
 3. The method of claim2 wherein the emulsion of wax in water is applied by spraying.
 4. Themethod of claim 2 wherein the emulsion of wax is applied by immersion.5. The method of claim 1 wherein the hydrated calcium silicate body isof a density of about 8 to about 16 pounds per cubic foot.
 6. The methodof claim 1 wherein the said wax is montan wax.
 7. A soft and porous lowdensity body comprising hydrated calcium silicate having on a surfacethereof a noncontinuous deposition of wax having a melting point of atleast about 170* F. and in amounts of about 0.1 to about 0.5 gram persquare foot of said surface area.
 8. The soft and porous low densitybody of claim 7 which comprises hydrated calcium silicate of a densityof about 5 to 30 pounds per cubic foot and comprises up to about 25percent of reinforcing asbestos fiber and wherein said wax is selectedfrom the group consisting of montan wax, ouricury wax, palm wax, sugarcane wax and a wax produced by the hydrogenation of castor oil.
 9. Thesoft and porous low density hydrated calcium silicate body of claim 7which is of a density of about 8 to 16 pounds per cubic foot andcomprises reinforcing fiber.
 10. The soft and porous low densityhydrated calcium silicate body of claim 7 wherein the wax applied ismontan wax.